Various types of distillate fuel oils such as diesel fuels, various oils of lubricating viscosity, automatic transmission fluids, hydraulic oil, home heating oils, and crude oils require the use of pour point depressant additives in order to allow them to flow freely at lower temperatures. The use of such additives has been known for some time. For example, U.S. Pat. No. 1,667,214 to Michel discloses the use of a fuel additive which includes a mono-alkyl-naphthalene and a poly-alkyl-naphthalene. The additives disclosed within the patent are produced by alkylating naphthalene in the presence of an aluminum chloride catalyst.
U.S. Pat. No. 1,815,022 to Davis discloses a similar additive which is comprised of naphthalene substituted with a chlorinated wax. The chlorinated wax is added to the naphthalene in the presence of an aluminum chloride catalyst.
The pour point depressants, as disclosed by Michel and Davis, were utilized in oils which included higher amounts of kerosene than is normally present in such oils today. Kerosene acts as a solvent for the wax present in distillate fuel oils. However, demands for kerosene for use in jet fuels has caused the amount of kerosene present in distillate fuel oils to be decreased over the years. This, in turn, has required the addition of wax crystal modifiers which are increasingly efficient in order to make up for the lack of the kerosene.
An additive combination for cold flow improvement of distillate fuel oils is disclosed within U.S. Pat. No. 3,910,776 to Feldman. The combination includes alkyl aromatics which are the condensation product of a chlorinated wax and naphthalene with an ethylene-containing polymer and an N-aliphatic hydrocarbyl succinimic acid.
U.S. Pat. No. 3,883,318 to Feldman, et al. discloses another pour point depressant which is comprised of a mixture of compounds such as a hydrogenated wax aromatic pour point depressant, a hydrogenated alkyl aromatic fraction of an amorphous normal solid wax and an ethylene backbone pour point depressant.
U.S. Pat. No. 4,255,159 to Miller, et al. contains the disclosure of an additive which is a mixture of different types of cold flow property improving compounds. The additive is disclosed as having synergistic flow and filterability improving properties with respect to fuel oils. The additive may be comprised of:
(1) a polymer of isomerized monoolefins or the alkylation product of naphthalene with the polymeric monoolefin, and
(2) the condensation product of a chlorinated paraffin and an aromatic hydrocarbon which may also be naphthalene.
This combination of two different types of substituted naphthalene compounds used as a fuel additive is indicated as having synergistic effects with respect to improving the cold flow and filterability properties of present day fuel oils.